Abstract
Abstract Metal electrode corrosion driven by halide migration and interfacial defects remains a significant bottleneck limiting the operational stability and photovoltaic performance of perovskite solar cells (PSCs), particularly in devices with varied bandgaps. Herein, we present a multifunctional interface engineering strategy by incorporating the IL 1‐butylpyridinium tetrafluoroborate (BPYBF 4 ) into the PCBM electron transport layer to simultaneously address these issues. The BF 4 − anions coordinate with the Ag + , forming a corrosion‐resistant layer that mitigates iodine‐induced degradation. Concurrently, the BPY + cations react with residual PbI 2 at the perovskite surface, inducing the formation of a 1D perovskite capping layer that effectively passivates interfacial defects and suppresses ion migration. Phase‐transition process during film conversion was systematically investigated, revealing a gradual transformation of residual PbI 2 into a protective 1D perovskite structure upon BPYBF 4 incorporation. Additionally, the presence of ionized PCBM enhances surface potential alignment, promoting efficient electron extraction and reducing non‐radiative recombination losses. This strategy demonstrates broad applicability—not only enhancing the performance of 1.55 eV normal‐bandgap PSCs but also achieving outstanding efficiency for wide‐bandgap PSCs, with PCEs of 22.69% for 1.67 eV and 18.60% (certified at 17.75%) for 1.85 eV, respectively. This work provides a facile and scalable approach to simultaneously protect the electrode and stabilize the perovskite films, offering a promising strategy for varied bandgaps PSCs in both single‐junction and tandem configurations. image